🧠 HNG-stage-one: String Analysis API

A minimalist Express.js backend for analyzing, storing, filtering, and deleting strings.
It supports palindrome detection, word counting, and natural language filtering using simple heuristics.
Everything is stored in a local JSON file — no database setup required.

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🚀 Features

• Create and analyze strings with rich metadata
• Retrieve single or multiple string entries
• Filter with structured or natural language queries
• Delete stored strings
• Persistent local JSON storage
• Color-coded logs for visibility

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🗂️ Project Structure

        string-analyzer-api/
      │
      ├── controllers/
      │ └── controller.js # All route logic (create, read, filter, delete)
      │
      ├── routes/
      │ └── routes.js # API routes mapped to controller methods
      │
      ├── utils/
      │ └── logger.js # Logging utilities
      │
      ├── stringsStore.json # Local JSON storage
      │
      ├── server.js # Express app entry point
      ├── package.json
      └── README.md

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⚙️ Setup & Installation

1. Clone the repository

git clone https://github.com/yourusername/string-analyzer-api.git
cd string-analyzer-api

2. Install dependencies

npm install express cors body-parser

3. Run the server

npm start

4. Development mode (auto-restart)

npm run dev

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🧩 API Endpoints

1. Create a String

POST /strings

Request Body

    {
      "value": "man of stones"
    }

Success Response – 201 Created

    {
      "id": "fcfc1723-1326-4d2f-8278-b4161af13775",
      "value": "man of stones",
      "properties": {
        "length": 13,
        "is_palindrome": false,
        "unique_characters": 9,
        "word_count": 3,
        "sha256_hash": "dce77f0279534f7699f89da44f164faf770e10925c265960f2ec499d63a0dfb2",
        "character_frequency_map": {
          "m": 1,
          "a": 1,
          "n": 2,
          "o": 2,
          "f": 1,
          "s": 2,
          "t": 1,
          "e": 1
        }
      },
      "createdAt": "2025-10-21T10:22:43.918Z"
    }

Error Responses:

• 400 Bad Request – Missing or invalid body field
• 409 Conflict – String already exists

2. Get All Strings

GET /strings

Success Response – 200 OK

    {
      "data": [ /* all stored strings */ ],
      "count": 3
    }

3. Get a Specific String

GET /strings/:value

      Example:
      GET /strings/man%20of%20stones

Success Response:

    {
      "id": "fcfc1723-1326-4d2f-8278-b4161af13775",
      "value": "man of stones",
      "properties": {
        "length": 13,
        "is_palindrome": false,
        "unique_characters": 9,
        "word_count": 3
      },
      "createdAt": "2025-10-21T10:22:43.918Z"
    }

Error Response:

• 404 Not Found – String does not exist in the system

4. Filter Strings (Structured Query)

GET /strings?is_palindrome=true&min_length=5&max_length=15

Supported Query Parameters:

Parameter	Type	Description
is_palindrome	boolean	Filter palindromic strings
min_length	number	Minimum string length
max_length	number	Maximum string length
word_count	number	Exact word count
contains_character	string	Must include a given character

Example Response:

    {
      "data": [ { "value": "racecar", "properties": { "is_palindrome": true } } ],
      "count": 1,
      "filters_applied": {
        "is_palindrome": "true",
        "min_length": "5",
        "max_length": "15"
      }
    }

5. Natural Language Filtering

GET /strings/filter-by-natural-language?query=<your query>

Success Response – 200 OK

    {
      "data": [ /* filtered results */ ],
      "count": 1,
      "interpreted_query": {
        "original": "all single word palindromic strings",
        "parsed_filters": {
          "is_palindrome": true,
          "word_count": 1
        }
      }
    }

Error Responses:

• 400 Bad Request – Unable to parse natural language query
• 422 Unprocessable Entity – Conflicting filters
• 404 Not Found – No matching string entries

6. Delete String

DELETE /strings/:value

Example:

DELETE /strings/man%20of%20stones

Success Response – 204 No Content

• (Empty response body)

Error Responses:

• 404 Not Found – String does not exist
• 400 Bad Request – Missing or invalid parameter